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Dynamo Activity in Strongly Magnetized Accretion Disks

Event Dates:

Seminar Location:

JILA 10th Floor - Foothills Room

Speaker Name(s):

Greg Salvesen

Speaker Affiliation(s):

CU Boulder

Seminar Type/Subject

Scientific Seminar Type:

Astrophysics Lunch Seminar

Event Details & Abstract:

The compelling observational evidence for strongly magnetized accretion disks around black holes and their attractive theoretical properties warrant an investigation into how such a disk magnetization state can develop and persist. The structure and evolution of these disks are governed by a dynamo-like mechanism, which channels part of the accretion power liberated by the magnetorotational instability (MRI) into an ordered toroidal magnetic field. To study this dynamo activity, we performed a suite of accretion disk simulations in the local limit ( i.e., shearing boxes). We find that the entire disk develops into a magnetic pressure-dominated state for a sufficiently strong net vertical magnetic flux and dynamo activity persists. Still stronger fields result in a highly inhomogeneous disk structure, with large density fluctuations. Finally, we show that the magnetized state of the disk in our simulations is well-matched by an analytic model describing the creation and buoyant escape of toroidal field.

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JILA is a joint physics institute of the University of Colorado at Boulder and the National Institute of Standards and Technology. We support an eclectic and innovative research program that fosters creative collaborations among our scientists. Collaborations play a key role in the pioneering research JILA and the JILA Physics Frontier Center are known for around the world. To learn more, visit our About JILA page.